Disposable diapers with elastically contractible waistbands

ABSTRACT

Disposable diapers having elasticized waistbands which allow the diapers to breathe and which reduce the incidence of waistband rollover. The waistbands are formed by affixing elastic elements between the topsheets and the backsheets (in the waistband region of the diapers) using regularly spaced, transversely extending regions of securement. Regions of nonsecurement are formed between pairs of the regions of securement thereby forming channels which allow the diaper to breathe and also forming corrugations which tend to inhibit waistband rollover.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention concerns disposable diapers, incontinent briefs, and thelike having elastically contractible waistbands.

2. Background Art

Infants (and other incontinents) wear disposable diapers to receive andcontain urine, feces, and other body fluids. Disposable diapers functionboth to contain the discharged materials and to isolate these materialsfrom the body of the wearer and from the wearer's surroundings. Modernembodiments of disposable diapers frequently perform these tasks in amanner superior to that of traditional cloth diapers.

Disposable diapers normally comprise three elements: a liquid permeabletopsheet designed to be placed next to the wearer's skin; a liquidimpermeable backsheet which forms, in use, the outer surface of thediaper; and an absorbent element interposed between the topsheet and thebacksheet.

The topsheet is frequently a hydrophobic non-woven fabric which isreadily permeable to fluid. Its hydrophobicity tends to cause thesurface in contact with the wearer's skin to be dry and protected fromfluids absorbed within the absorbent element.

The absorbent element receives and retains fluids which pass through thetopsheet. It normally comprises a batt of airlaid wood pulp fibers.

The backsheet functions to contain fluids within the absorbent elementthereby protecting the wearer's outer garments and other surfaces fromsoiling by these fluids. Backsheets are commonly formed of fluidimpermeable, vapor impermeable material such as polyethylene film.

Disposable diapers having many different basic designs are known to theart. For example, Duncan and Baker in U.S. Pat. No. Re. 26,152, issuedJan. 31, 1967, describe and claim a disposable diaper which has achievedwide acceptance and commercial success. Buell, in U.S. Pat. No.3,860,003, issued Jan. 14, 1975, describes and claims another disposablediaper which, too, has achieved wide acceptance and commercial success.The diaper taught by Buell differs from that taught by Duncan and Bakerin many respects, not the least of which is the provision in the Buelldiaper of elasticized (or contractible) leg cuffs. Another embodiment ofdisposable diapers is described and claimed by Aziz and Blaney inEuropean Patent Application No. 82200801.7, filed June 29, 1982. TheAziz and Blaney diaper also provides elasticized (or contractible) legcuffs, but is of a somewhat different design than that described byBuell.

Mesek et al in U.S. Pat. No. 4,324,245, issued Apr. 13, 1982; Pieniak etal in U.S. Pat. No. 4,337,771, issued July 6, 1982; and Mesek et al inU.S. Pat. No. 4,352,355, issued Oct. 5, 1982 describe disposable diapershaving elasticized cuffs and elasticized (or contractible) waistbands.

Strickland and Visscher in U.S. Pat. No. 4,253,461, issued on Mar. 3,1981, describe and claim another form of disposable diaper sometimesreferred to as an incontinent brief and intended to be worn by adults.

While the disposable diapers described above, particularly thosedescribed by Duncan and Baker, Buell, and Aziz and Blaney, function inexemplary manners, disposable diapers comprising fluid and vaporimpermeable backsheets have sometimes been perceived as being somewhathot and uncomfortable. Further, diapers provided with such impermeablebacksheets are unable to self-dry as they otherwise would becauseevaporation of fluids from the absorbent element is precluded. Tocounteract this perception, and to permit self-drying, backsheets whichare relatively impermeable to liquid but relatively permeable to vaporand which are known as breathable backsheets have been described.Breathable backsheets tend to provide a cooler garment and permit somemeasure of self-drying of the diaper while it is being worn. Forexample, Crowe, Jr. in U.S. Pat. No. 3,156,242, issued on Nov. 10, 1964,teaches the use of a microporous film as a breathable backsheet.Hartwell, in U.S. Pat. No. 3,881,489, issued on May 6, 1975, teaches abreathable backsheet comprising, in combination, two layers: a low-voidvolume perforated thermoplastic film and a porous high-void volumehydrophobic tissue. Sisson, in U.S. Pat. No. 3,989,867, issued on Nov.2, 1976, teaches a breathable backsheet provided with tapered hollowedbosses which prevent the passage of liquid while allowing vapor to passreadily therethrough. Obenour, in U.S. Pat. No. 4,341,216, issued July27, 1982, describes and claims a still different embodiment of abreathable backsheet.

The above cited ten patents and patent application are incorporatedherein by reference.

While breathable backsheets do provide an improvement over the morecommon liquid and vapor impermeable backsheets, and while thosedescribed in the patents to Sisson, Hartwell and Obenour are ofparticular value, developments providing for more comfortable and moreserviceable diapers have still been sought.

SUMMARY OF THE INVENTION

The present invention is of a disposable diaper comprising anelastically contractible waistband which allows the diaper to breath andwhich tends to resist waistband rollover. These benefits are achieved byproviding disposable diapers with a waistband comprising an elasticelement interposed between the topsheet and the backsheet and affixed toboth the topsheet and the backsheet in such a way as to cause theformation of transverse channels between the topsheet and the elasticelement. Transverse in this context means extending across ("transverseto") the waistband and that the channels which are formed between thetopsheet and the elastic element and between the backsheet and theelastic element extend from the outer diaper margin to an interiorregion of the diaper.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a disposable diaper embodying thepresent invention and in a configuration as applied to an infant.

FIG. 2 is a partially fragmented plan view of the disposable diapershown in FIG. 1 in an unfolded configuration.

FIG. 3 is an enlarged partial view of the waistband of the diaper ofFIG. 1 illustrating one embodiment of the present invention.

FIG. 4 is an enlarged partial view of the waistband of the diaper ofFIG. 1 illustrating another embodiment of the present invention.

FIG. 5 is an end view of the portion of the waistband of the disposablediapers shown in FIGS. 3 and 4.

DETAILED DESCRIPTION OF THE INVENTION

While this specification concludes with claims particularly pointing outand distinctly claiming the subject matter regarded as the invention, itis believed that a better understanding of the invention can be achievedthrough careful reading of the following detailed description of theinvention in conjunction with study of the attached drawings and theappended example.

Disposable diapers comprise three major elements: a topsheet; abacksheet; and an absorbent element. The topsheet forms the inside ofthe disposable diaper (i.e., that portion intended to be placed next tothe wearer's skin). The backsheet generally forms the exterior surfaceof the disposable diaper. The absorbent element is interposed betweenthe topsheet and the backsheet.

A disposable diaper is generally designed to be placed between andgenerally centered between the legs of an infant and secured about theinfant by bringing the front portion of the diaper adjacent the frontwaist area of the infant and the rear portion of the diaper adjacent therear waist area of the infant and securing the diaper in that position.

Optionally, disposable diapers comprise fastening tapes for securing thediaper about the infant. They also optionally comprise elastic membersin the longitudinally extending margins to form an elasticallycontractible leg cuff or side flap. They also optionally compriseelastic elements in the laterally extending margins to form elasticallycontractible waistbands.

The waistband of a disposable diaper is that portion of the diaper whichis intended to be placed adjacent the wearer's waist. While thewaistband can comprise a separate element affixed to the body of thedisposable diaper, it more often is an extension of other elements ofthe disposable diaper such as the backsheet or the topsheet or both thebacksheet and the topsheet. Further, the waistband is generallyconsidered to be that portion of the diaper extending from the laterallyextending margin of the diaper to about the laterally extending marginof the absorbent element. Disposable diapers are normally constructed soas to have two waistbands: a front and rear. While disposable diaperscan be constructed so as to have a single unitary waistband encirclingthe waist of the wearer, such designs are not preferred. It is alsopossible to construct a disposable diaper having three or more waistbandsections intended to be affixed about the waist of the wearer, but,these embodiments, too, are not preferred.

The present invention provides a disposable diaper having at least oneelastically contractible waistband. The waistband comprises an elasticelement interposed between the topsheet and the backsheet andcontractibly affixed to both the topsheet and the backsheet bytransverse regions of securement. The transverse regions of securement,which are preferably essentially regularly spaced, define between eachpair thereof a transverse region of nonsecurement extending from theouter margin of the waistband (which is the laterally extending marginof the diaper) essentially completely across the width of the elasticelement. These transverse regions of nonsecurement exist between thetopsheet and the elastic element and between the backsheet and theelastic element.

The phrase "contractibly affixed" means that the elastic element isaffixed to the topsheet and to the backsheet when the elastic element isin an elongated orientation relative to its relaxed or contractedorientation and that when the elastic element is allowed to assume itsrelaxed or contracted orientation, the topsheet and the backsheet aregathered or shirred, usually in a regular, frequently predictable,manner.

FIG. 1 is a perspective view of a disposable diaper embodying thepresent invention. While the diaper illustrated in FIG. 1 is based onthe disposable diaper design taught in the hereinbefore incorporatedpatent to Buell, and while this is a preferred diaper design for the useof the present invention, it must be realized that the present inventioncan be used, and is contemplated for use, with other disposable diaperdesigns. Several such designs are described in the hereinbeforeincorporated patents and European patent application, but other designscan be readily envisioned by those skilled in the art. The Buell designhas been selected to exemplify the present invention because it is apreferred design.

Referring now to FIG. 1, disposable diaper 10 is shown in perspective ina configuration as if it were applied about an infant. Disposable diaper10 comprises a front portion 11 and a rear portion 12 with a crotchportion 13 interposed therebetween. In use, crotch portion 13 is placedbetween the legs of the infant and front portion 11 and rear portion 12are placed, respectively, along the front and rear lower portions of thewearer's trunk. Topsheet 15 forms the inner surface of disposable diaper10 while backsheet 14 forms its outer surface. Side flaps (or leg cuffs)16 fit about the wearer's thighs. In use, front waistband 17 and rearwaistband 18 are placed adjacent the wearer's waist regions on,respectively, the front and rear portions of the wearer's trunk.Disposable diaper 10 is held in position about the wearer by fasteningtape 19. Outer margin of waistband 29 is shown in FIG. 1 as the upperedge of disposable diaper 10. Transverse regions of securement 25 andtransverse regions of nonsecurement 26 in the waistbands are discussedmore fully hereinafter.

It must be noted that reference numerals are used consistentlythroughout all the figures and that the thicknesses of certain materialsin the figures have been exaggerated for clarity.

FIG. 2 is a partially cut away plan view of disposable diaper 10 openedout into a planar configuration. Topsheet 15 is, in this illustration,the upper surface of the diaper while backsheet 14 is the lower surface.Absorbent element 21 is interposed between topsheet 15 and backsheet 14.

As illustrated, disposable diaper 10 is generally symmetrical aboutlongitudinal center line 27 and lateral center line 28. While this is apreferred configuration, it is not necessary that disposable diaper 10be symmetrical. An asymmetric orientation about lateral center line 28,as when crotch portion 13 is transposed toward front waistband 17, isquite useful.

Disposable diaper 10 is provided with elastic members 22 in the sidemargins thereof running generally parallel to longitudinal center line27. In the embodiment illustrated, two elastic members 22 are placed oneither side of disposable diaper 10; single or multiple elastic memberscan be used. The embodiment illustrated is, however, preferred.

Fastening tapes 19 are secured to disposable diaper 10 adjacent rearwaistband 18.

Front elastic waist element 23 and rear elastic waist element 24 arepositioned, respectively, in front waistband 17 and rear waistband 18adjacent outer margin of waistband 29. In the embodiment illustrated inFIGS. 1 and 2, disposable diaper 10 comprises elastic waist elements inboth the front and the rear waistbands. While this is a preferredembodiment, the present invention is useful in diaper designs havingonly the front or only the rear waistband elasticized.

Transverse regions of securement 25 and transverse regions ofnonsecurement 26 are also illustrated in FIG. 2.

One major function of backsheet 14 is to prevent body fluids fromescaping from disposable diaper 10 and soiling the wearer's outergarments and other surfaces in contact with the disposable diaper. Anycompliant, non-irritating planar material which is impermeable to bodyfluids can be used as backsheet 14. Suitable materials are describedwith particularity in the hereinbefore incorporated patents and patentapplication. A preferred backsheet is formed from polyethylene filmhaving a thickness of from about 0.012 to about 0.051 millimeter (mm).

Breathable backsheets (i.e., backsheets that permit the passage of vaporand air while retarding the passage of liquid) useful in the presentinvention are described in the hereinbefore incorporated patents toCrow, Jr., Hartwell, Sisson, and Obenour.

The size of backsheet 14 is dictated by the exact diaper design selectedand the size of the infant intended to be the wearer; it can be readilyascertained by those skilled in the art.

Topsheet 15 can be any compliant, soft feeling, non-irritating (to thewearer's skin) planar material. It functions to contact the wearer'sskin, to receive fluid discharges, to allow the discharges to passreadily therethrough into the absorbent element, and to isolate thewearer's skin from the fluids in the absorbent element. To aid ineffective performance of the last function, the topsheet is preferablyhydrophobic.

Topsheet 15 can be porous paper made from natural or synthetic fibers ormixtures thereof, non-woven fabric made from natural or synthetic fibersor mixtures thereof, apertured plastic film, porous foam, or the like.Examples of suitable topsheets are described in the hereinbeforeincorporated patents and patent application.

A preferred topsheet is spun bonded non-woven polyester fabric made fromfibers of from about 2.2 to about 2.5 denier, having a basis weight ofabout 17 grams (g) per square meter (M²). Another preferred topsheetmaterial has a basis weight of 22 g per M² and comprises about 65% (byweight) staple length, 1.5 denier polyester fibers (such as Kodel type411 polyester fibers as sold by Tennessee Eastman Corporation,Kingsport, Tenn.); about 15% crimped, staple length, 1.5 denier rayonfibers; and about 20% acrylic copolymer binder (such as Celanese CPE8335 as sold by Celanese Corporation of Charlotte, N.C.). "Staplelength" refers to fibers having a length of at least about 15 mm.

Still another preferred topsheet is constructed from polypropylenefibers which have been carded and thermally bonded in a spaced-apartpattern. Fibers about 3.8 centimeters (cm) long and of from about 1.5 toabout 3.0 denier are suitable. A preferred topsheet of this type has abasis weight of about 24 g per M².

Suitable topsheets can also be constructed from apertured plastic filmssuch as those described by Radel and Thompson in U.S. Pat. No.4,342,314, issued Aug. 3, 1982; Ferguson and Landrigan in U.S. Pat. No.4,341,217, issued July 27, 1982; and Thompson in U.S. Pat. No.3,929,135, issued Dec. 30, 1975. These three patents are incorporatedherein by reference.

As with the case of backsheet 14, the size of topsheet 15 is dictated bythe exact diaper design selected.

Absorbent element 21 can be any means which is generally compressible,conformable, non-irritating to the wearer's skin, and which is capableof absorbing and retaining fluids.

Absorbent element 21 can be constructed from any of a variety ofmaterials commonly used in disposable absorbent articles and which aredescribed in the hereinbefore incorporated patents. Examples of suitableabsorbent materials include creped cellulose wadding, absorbent foams,absorbent sponges, super absorbent polymers, and, preferably, comminutedand airlaid wood pulp fibers commonly referred to as absorbent fluff. Anabsorbent fluff having a density of from about 0.05 to about 0.175 g percm³ is generally acceptable.

As in the case of backsheet 14 and topsheet 15, the size of absorbentelement 21 is dictated by the exact diaper design selected.

Optionally, absorbent element 21 can have associated with either or bothplanar faces envelope tissues (not illustrated in the drawings)comprising any permeable material well known to those skilled in theart, such as wet strength tissue paper. When used, envelope tissues aregenerally coextensive with absorbent element 21 and either coterminustherewith or folded up and about the laterally extending marginsthereof. Envelope tissues can optionally be secured to absorbent core 21by any means well known to those skilled in the art.

Absorbent element 21 is interposed between backsheet 14 and topsheet 15.The diaper design selected determines whether or not the three elementsare coterminus although, in general, either backsheet 14 or topsheet 15or both extend beyond the margins of absorbent element 21. In thepresent invention, both backsheet 14 and topsheet 15 extend beyond thelaterally extending margins of absorbent element 21 and are essentiallycoterminus along their laterally extending margins.

Optionally, backsheet 14 can be secured to absorbent element 21 by anyconvenient means (not illustrated in the drawings) well known to thoseskilled in the art. Examples of suitable means are parallel beads ofadhesive (such as hot melt adhesive) and double sided adhesive tape;each extend essentially the entire longitudinal length of absorbentelement 21.

Elastic members 22 serve to contract or gather the cuffs (longitudinallyextending margins) of disposable diaper 10 and maintain them in contactwith the legs of the wearer thereby providing improved fit and reducingfluid leakage from the diaper. One material which can be used forelastic elements 22 is an elastic tape having a cross section of about0.18 mm by from about 1.5 mm to about 6.4 mm and made from naturalrubber as available from East Hampton Rubber Company of Stuart, Va.,under the trademark L-1900 Rubber Compound. Other suitable elasticmembers can be made from natural rubber elastic tapes sold under thetrademarks Fulflex 9211 and Fulflex 9111 by Fulflex Company, ofScotland, N.C.

The length of elastic elements 22 is dictated by the precise diaperdesign chosen. In the design illustrated in FIGS. 1 and 2, elasticelements 22 extend a major portion of the longitudinal length ofdisposable diaper 10, but terminate outside the waist regions ofdisposable diaper 10.

Elastic members 22 are operably associated with disposable diaper 10 bysecuring them to the diaper adjacent its longitudinally extendingmargins by elastic attachment means which are not shown in the Figures.The elastic attachment means should be flexible and of sufficientadhesiveness to hold elastic members 22 in their stretched conditionsubstantially indefinitely. One suitable means is hot melt adhesive. Amore detailed description of the manner in which elastic members 22should be positioned and secured to disposable diaper 10 is given in thehereinbefore incorporated patent to Buell.

Elastic members 22 are affixed to disposable diaper 10 in an elasticallycontractible condition so that in a normally unrestrained configurationelastic members 22 effectively contract or gather the diaper materialadjacent elastic members 22. Elastic members 22 can be affixed todisposable diaper 10 in an elastically contractible condition in atleast two ways. For example, elastic members 22 can be stretched to anelongated orientation and affixed to disposable diaper 10 whiledisposable diaper 10 is in an uncontracted condition. Alternatively,disposable diaper 10 can be contracted (in crotch portion 13, forexample by pleating) and elastic members 22 can be affixed to thecontracted disposable diaper 10 while the elastic members are in theirrelaxed or unstretched orientation.

Front waist element 23 and rear waist element 24 can be formed from thesame materials as elastic members 22, but, at the option of the diaperdesigner, can be constructed of different materials. Preferably, elasticwaist elements 23 and 24 are formed of elastic films having an elasticmodulus of from about 3.5 to about 30 kilograms per cm². Examples ofsuitable materials include ABA block copolymers of polystyrene andpolyolefin with alphamethyl styrene added. These materials are soldunder the Kraton trademark by Shell Chemical Company of Houston, Tex.Still another example of suitable films are those formed from ethylvinyl acetate by Exxon Chemical Company of Florham Park, N.J. Waistelastic elements 23 and 24 are at least about 0.6 cm wide, preferably atleast about 1.6 cm wide. While the maximum width of the elastic waistelements 23 and 24 is determined by the diaper design and matters ofeconomy, they generally are no wider than about 3.8 cm.

In the embodiment illustrated in FIGS. 1 and 2 elastic waist elements 23and 24 each extend across essentially the entire lateral width ofdisposable diaper 10. While this is a preferred construction, thepresent invention is useful in designs wherein elastic waist elements 23and 24 extend across only a portion of the lateral width of the diaper.Preferably, elastic waist elements 23 and 24 extend across a majorportion of the lateral width of disposable diaper 10.

Elastic waist elements 23 and 24 are contractibly affixed to both thetopsheet and the backsheet in front waistband 17 and rear waistband 18by transverse regions of securement. Elastic waist elements 23 and 24can be contractibly affixed in waistbands 17 and 18 by individuallyextending elastic waist elements 23 and 24 to elongated orientations,affixing elastic waist elements 23 and 24 to both topsheet 15 andbacksheet 14 while topsheet 15 and backsheet 14 are in an uncontractedorientation, and allowing elastic waist elements 23 and 24 to assumetheir relaxed or contracted orientation.

Alternatively, elastic waist elements 23 and 24 can be formed frommaterials which contract unidirectionally and become elastic followingspecific treatment such as heating. Elastic materials are known whichcan be heated to their transition temperature and stretched into anelongated orientation. They are then chilled and become relativelyinelastic and fixed in their elongated orientation. Subsequent heatingcauses the materials to contract to their initial (uncontracted orrelaxed) orientation and to regain their elasticity. Examples of suchmaterials are shown in U.S. Pat. No. 3,819,401, issued June 25, 1974 toMassengale et al and U.S. Pat. No. 3,912,565, issued Oct. 14, 1975 toKoch et al, both incorporated herein by reference. When such materialsare used as elastic waist elements, the topsheet, backsheet, and theelastic waist element are affixed together by transverse regions ofsecurement while all three are in uncontracted orientations. The systemis then heated (as with heated air) and the elastic waist element isallowed to return to its relaxed or contracted orientation.

Transverse regions of securement 25 are shown in a generalizedrepresentation in FIGS. 1 and 2. More specific embodiments of transverseregions of securement 25 are depicted in FIGS. 3 and 4 which areenlarged views of a portion of rear waistband 18 indicated by referencenumeral 3 in FIG. 2.

In this discussion of FIGS. 3 and 4, reference shall be made to rearwaistband 18 and the components thereof. The same comments can be madeabout front waistband 17 and its components since the two waistbands canbenefit from use of the present invention.

Transverse regions of securement 25 extend essentially across the wholewidth of elastic waist element 24.

The term "transverse" as used in this context refers to an orientationgenerally perpendicular to the major laterally extending dimension ofwaistband 18. That is to say, since rear waistband 18 extends laterallyacross the width of disposable diaper 10 and is generally parallel tolateral center line 28, the transverse regions of securement 25 extendacross rear waistband 18 in an orientation essentially parallel tolongitudinal center line 27; they are directed generally from outermargin of waistband 29 to the center of disposable diaper 10. Asillustrated, transverse regions of securement 25 are shown to be atessentially right angles to lateral center line 28 and to the lateralextent of waistband 18. This is the preferred orientation. One can,however, depart from true transversity without departing from the scopeand spirit of this invention. The departure from true (or absolute)transversity becomes too great when channels (as hereinafter discussed)are no longer formed extending essentially across the width of waistband18. In general, departure from transversity becomes too great forpractical operation of the present invention when the departure fromtransversity exceeds about 45° from true transversity (orperpendicularity to longitudinal center line 27).

The term "essentially across" is used in this context to indicate thattransverse regions of securement 25 need not extend absolutely acrossthe entire width of elastic waist element 24 so long as they extendsufficiently far across the width thereof to provide the channelsdiscussed hereinafter.

In FIG. 3, transverse regions of securement 25 are shown as essentiallyregularly spaced unitary zones of sealing attaching elastic waistelement 24 to topsheet 15 and backsheet 14 which is not visible in FIG.3 or 4. The precise means for providing the zones of sealing can bereadily selected by those skilled in the art. Examples include adhesiveattachment, heat sealing, solvent sealing and the like. Preferably,ultrasonic welding is used.

As illustrated in FIGS. 3, 4 and 5, the points of attachment of bothtopsheet 15 and backsheet 14 to elastic waist element 24 are in register(i.e. are coextensive). This is a preferred orientation, but the pointsof attachment of topsheet 15 to elastic waist element 24 can be offsetfrom the adjacent points of attachment of backsheet 14 to elastic waistelement 24. In such a situation there will be offset transverse regionsof securement on either side of the elastic waist element.

FIG. 4 illustrates an alternate embodiment of transverse regions ofsecurement 25'. In this embodiment, the transverse regions of securementcomprise discrete spaced zones of sealing, preferably ultrasonic welds,effectively attaching the materials together and forming the channelshereinafter described. Preferably the discrete spaced zones are circularor elliptical.

Transverse regions of securement 25 can be from about 0.15 to about 1.0cm wide (i.e. in the dimension generally parallel to lateral centerline28. They are preferably regularly spaced, but they can be nonuniformlyspaced. They are preferably from about 0.3 to about 1.5 cm apart asmeasured from center to center.

FIG. 5 illustrates the functioning of this invention. FIG. 5 is an endview of the portions of rear waistband 18 shown in FIG. 3 and FIG. 4with rear elastic waist element 24 in a relaxed or contracted position.In FIG. 5, transverse regions of securement 25 are shown as darkenedportions for emphasis. Since rear elastic waist element 24 is in itsrelaxed or contracted position, topsheet 15 and backsheet 14 are showngathered. These gathers constitute and define transverse regions ofnonsecurement 26b between backsheet 14 and rear elastic waist element 24and transverse regions of nonsecurement 26t between topsheet 15 and rearelastic waist element 24. These transverse regions of nonsecurement 26band 26t form open gathers or channels from the margin of the diaperextending to the interior of the diaper and terminating in the regionadjacent the laterally extending edges of absorbent element 21. Theseopen channels allow the diaper to breathe by allowing the exchange ofair and vapor between the interior of the diaper and the surroundingatmosphere even when the diaper is secured about an infant.

When rear elastic waist element 24 is expanded to an elongatedorientation, as when disposable diaper 10 is fastened about an infant,the channels decrease in size. This variation in size gives the personapplying the diaper to the wearer some measure of control over theamount of breathability as by stretching the elasticized waistbands togreater or lesser extents when securing the diaper about the infant.Further, since open channels can occasionally allow liquid to leak fromabsorbent element 21, the ability to adjust the size of the channelsgives some measure of control over the maximum extent of leakage whichwill be permitted.

At the same time as transverse regions of nonsecurement 26b and 26t areformed, topsheet 15 and backsheet 14 form structures in the nature ofcorrugations. These corrugations extend transversely across the width ofrear waistband 18 tend to stiffen the waistband thereby tending toprevent waistband rollover (i.e., the bending of the waistband aboutitself).

EXAMPLE

Diapers according to the present invention were constructed followingthe basic design described in the aforementioned patent to Buell. Thisdiaper design provided for two (front and rear) waistbands.

The absorbent element comprised absorbent fluff having a density ofabout 0.09 g per cm³ and a basis weight of about 650 g per M². It wasgenerally hourglass-shaped and was about 40 cm long, about 26.7 cm wideat each of its laterally extending margins, and about 9.5 cm wide in thecrotch portion. It was symmetrical about its longitudinal center line,but asymmetrical about its lateral center line in that the crotchportion was centered about 21.1 cm from the rear lateral margin.

The topsheet comprised the thermally bonded polypropylene materialhereinbefore mentioned and the backsheet 0.04 mm thick polyethylenefilm. Both also were hourglass-shaped and were about 45.1 cm long andabout 31.8 cm wide at their laterally extending margins.

During construction, the absorbent element was interposed between thetopsheet and the backsheet which were essentially coextensive andcoterminus. Two-sided adhesive tapes running parallel to thelongitudinal center line secured the backsheet to the absorbent element.They also secured the backsheet to the topsheet in the cuff regions, butnot in the waistband regions.

The cuff portions of the diapers were elasticized by incorporatingtherein two elastic members in each longitudinally extending margin ofthe diaper at the crotch portion. Each was made of Fulflex 9111 and was6.4 cm wide and 0.18 cm thick; the inner one was 13.3 cm long, the outer15.2 cm. These elastic members were centered about the crotch portion.The pattern defined by the pair of members was centered about 11.7 cmfrom the longitudinal center line of the diaper and parallel thereto.The two elastic members in each diaper margin were centered on parallellines about 1.6 cm apart.

Each diaper waistband extended the lateral width of the diaper and wasabout 31.8 cm long; each waistband was about 2.5 cm wide in thetransverse direction. The elastic waist element used in each waistbandwas made by Clopay Corporation of Cincinnati, Ohio from apolystyrene-polyolefin block copolymer. Each was about 40.6 cm long,about 5.1 cm wide, and about 0.04 mm thick and was stretched to a lengthof about 49.5 cm prior to being secured to both the topsheet and thebacksheet. At the time of securement the topsheet and the backsheet werein fully extended configurations.

Transverse regions of securement comprising discrete zones of ultrasonicwelds were used to affix each elastic waist element to both the topsheetand to the backsheet. The transverse regions of securement eachcomprised six discrete elliptical zones of ultrasonic welds each havinga major axis of about 1.5 mm and a minor axis of about 0.8 mm; eachindividual ellipse was set with its major axis at an angle of about 45°to the transverse direction. The transverse regions of securement wereregularly spaced along each waistband and their centers were about 6.4mm apart.

Adhesive fastening tapes were adhesively affixed to the diaper.

When worn by infants, these diapers performed in a satisfactory mannerand the waistbands thereof tended to permit transfer of vapor from theinterior of the diaper to the surrounding atmosphere and thecorrugations formed in the waistband tended to prevent waistbandrollover.

What is claimed is:
 1. A disposable diaper having at least onewaistband, said diaper comprising a topsheet, a backsheet, and anabsorbent element interposed between said topsheet and said backsheetwherein at least one waistband comprises an elastic element interposedbetween said topsheet and said backsheet and contractibly affixed tosaid topsheet and to said backsheet by essentially regular transverseregions of securement defining therebetween transverse regions ofnonsecurement extending from the outer margin of said waistband acrossessentially the entire width of said elastic element.
 2. The diaper ofclaim 1 wherein said transverse regions of securement comprise unitaryzones of sealing.
 3. The diaper of claim 2 wherein said zones of sealingcomprise ultrasonic welds.
 4. The diaper of claim 1 wherein saidtransverse regions of securement comprise discrete, spaced apart zonesof sealing.
 5. The diaper of claim 4 wherein said zones of sealingcomprise ultrasonic welds.